1. Technical Field
The present invention relates to machine tools furnished with: a bed; a table on which workpieces are carried and which is installed on the bed; a spindle for retaining a tool, and, with its axis disposed horizontally, provided to rotatable centered on the axis; and a feed mechanism for moving the table and the main spindle relatively to each other along three orthogonal axes.
2. Description of the Related Art
Such machine tools known to date include the example illustrated in FIG. 5 and FIG. 6 (cf. Japanese Unexamined Pat. App. Pub. No. 2003-266257).
This machine tool 100 comprises: a bed 101; a table 102 for carrying a workpiece W and installed on the upper surface of the bed 101 along the front, movable back and forth (along the Z-axis); a column 103 stood on the upper surface of the bed 101 along the rear; a saddle 104 supported on a front face of the column 103, movable perpendicularly (along the Y-axis); a spindle head 105 supported on a front face of the saddle 104, transverse movable sideways (along the X-axis); a main spindle 106 for retaining a tool (not illustrated), and by the spindle head 105 being supported to be rotatable about the spindle axis, which is parallel to the Z axis; a Z-axis guide mechanism 110 for guiding Z-axis directed movement of the table 102; a Y-axis guide mechanism 111 for guiding Y-axis directed movement of the saddle 104; an X-axis guide mechanism 112 for guiding X-axis directed movement of the spindle head 105; a Z-axis feed mechanism 113 for moving the table 102 along the Z-axis; a Y-axis feed mechanism 114 for moving the saddle 104 along the Y-axis; and an X-axis feed mechanism 115 for moving the spindle head 105 along the X-axis.
Thus, by the table 102, the saddle 104, and the spindle head 105 being driven by the respective feed mechanisms 113, 114, and 115 and guided by the guide mechanisms 110, 111, and 112 to travel along the Z-axis, along the Y-axis, and along the X-axis, respectively, the workpiece W on the table 102 and the (not-illustrated) tool on the main spindle 106 are moved relative to each other along the three orthogonal axes directions to machine the workpiece W.
However, a problem with the conventional machine tool 100 has been that with the saddle 104 being supported on the front face of the column 103 and the spindle head 105 being supported on the front face of the saddle 104, the saddle 104 and spindle head 105 jut out toward the front face of the machine tool 100, on account of which deflection or similar deformation occurs in the column 103, the saddle 104, and the spindle head 105, which is prohibitive of precision-machining the workpiece W precisely.
Furthermore, the Z-axis guide mechanism 110 and the Z-axis feed mechanism 113 are provided on the top face of the bed 101, the Y-axis guide mechanism 111 and the Y-axis feed mechanism 114 on the front face of the column 103, and the X-axis guide mechanism 112 and the X-axis feed mechanism 115 on the front face of the saddle 104. In other words, the Z-axis guide mechanism 110, the Z-axis feed mechanism 113, the Y-axis guide mechanism 111, the Y-axis feed mechanism 114, the X-axis guide mechanism 112, and the X-axis feed mechanism 115 are arranged facing the work area where the workpiece W is machined. Consequently, even though the Z-axis guide mechanism 110, the Z-axis feed mechanism 113, the Y-axis guide mechanism 111, the Y-axis feed mechanism 114, the X-axis guide mechanism 112, and the X-axis feed mechanism 115 are covered with suitable covers (not illustrated), chips generated during the machining of the workpiece W are likely to intrude into the covers such that maintenance on the covers has to be performed frequently, or expensive covers of complex structure have to be employed.
Furthermore, with the column 103 being situated along the rear portion of the bed 101, the Y-axis guide mechanism 111, the Y-axis feed mechanism 114, the X-axis guide mechanism 112, and the X-axis feed mechanism 115 are situated on the rear portion of the bed 101, a consequent problem has been that performing maintenance on the Y-axis guide mechanism 111, the Y-axis feed mechanism 114, the X-axis guide mechanism 112 and the X-axis feed mechanism 115 is difficult.
In addition, the machine tool 100 typically comprises a tool changer made up of a tool magazine for accommodating a plurality of tools, and an exchange mechanism, among other components. The exchange mechanism is provided at one end with an exchange arm having a grabber for grasping a tool housed in the tool magazine, and at the other end with a grabber for grasping the tool retained by the spindle 106, whereby the tool in the tool magazine and the tool retained by the spindle 106 can be exchanged by rotating the exchange arm about its rotational center axis paralleling the Z axis and meanwhile moving it along the Z-axis. However, if the installation footprint for the machine tool 100 is restricted widthwise (along the X-axis), the tool magazine and the exchange mechanism cannot be disposed on the lateral flanks of the bed 101, which leads to the tool magazine and exchange mechanism being disposed on the upper surface of the column 103. A problem with this situation has been that while the tool magazine and the exchange mechanism, jutting out toward the tip of the spindle 106, have to be supported by suitable support members, because the tip of the spindle 106 and the column 103 are separated in the Z-axis direction the support structure is destabilized.